Ele/Cold Templar Build (pls comment)

Hello together,
i want to build a Templar with fokus on AoE cold damage:

68 Passives

Because i'm fokusing on AoE-Damage i set on Cast Speed instead of Spell Crit.

First Gems i want to use:
Main AoE
Ice Nova

To attac individuals
Freezing Pulse

To handle Aggro
Decoy Totem

Against cold damage immune mobs
Fireball
Firestorm

Can someone give me a feedback if i can go on with this build? Mny thx :)